Several publications show cellular shades, wherein a fabric material is formed to define parallel tubular cells extending horizontally across the width of the shade. Air within each of the cells only circulates minimally, such that when expanded the shade provides good thermal insulation.
It is of course desirable to make the physical appearance of the shade as attractive as possible. Similarly, it is desirable to make such shades as economically as possible, which requires both that a minimal amount of material be used to form each cell and that the manufacturing process be as expeditious as possible.
Various exemplary prior art disclosures include the following:
French patent 1,568,745 to Landa (which has Netherlands and West German equivalents) discloses a screen wherein a plurality of strips of a fabric material are folded about fold lines extending longitudinally and bonded together, the two edges of each strip being bonded to the center of the successive strip, to form a shade consisting of a plurality of tubular cells. The Landa screen is intended to be used such that the cells extend vertically. Landa teaches symmetrical cell shapes only.
U.S. Pat. No. 4,347,887 to Brown shows a "thermal shutter". A wide band of material is folded transversely to form a double row column of adjacent cells, which may have rounded visible contours. The cells are adhesively bonded to one another. The Brown structure is symmetrical, so that both sides of the shade thus formed have essentially the same appearance.
U.S. Pat. No. 4,450,027 to Colson shows a method and apparatus for fabricating a multiple cell shade wherein a continuous relatively narrow strip of fabric is sharply creased longitudinally in order to define pleats in the shade material. A U-shaped cell structure is thus formed. Successive cells are assembled by applying an adhesive to opposed edges of the folded strips, and adhering each formed strip to the strip making up the next preceding cell. The Colson patent discloses strips that are sharply creased to facilitate the formation of the cells.
U.S. Pat. Nos. 4,631,217, 4,676,855 and 4,677,013 to Anderson show in FIG. 3 a shade of asymmetrical construction. A rear wall section of each cell is essentially straight or linear when the shade is in its expanded position. The width of these rear wall sections thus defines the spacing of the adjacent cells, while the front of each cell, containing more material, maintains a non linear shape.
The Anderson patent also discloses a method of forming an expandable and collapsible shade consisting of an assembly of horizontal parallel cells, in which the cell structure is formed from a material folded into a Z-shape rather than from the U-shaped material shown in the Colson patent.
U.S. Pat. No. 4,846,243 to Schneider shows a foldable window covering formed of a wide relatively soft material folded transversely, as in the Brown patent, to yield a collapsible shade. The front surface of the shade consists of a number of drooping loops formed by doubling the material back on itself. The successive cells are spaced in the expanded position of the shade by a relatively vertical rear wall section of each cell. The Schneider construction is relatively complex and requires a large amount of material per cell. Furthermore, since the Schneider shade is formed of a wide strip of material folded transversely, this limits the width of the shade which can thus be formed to the width of the stock material available.